This invention relates to improvements in sealing elements designed for use at the joint between a rotating through shaft and a fixed wall or partition. The sealing device has particular application in military vehicle compartments, where it may be necessary to exclude external noxious or toxic chemicals from the interior personnel compartment. It is known to provide moving seals to seal the opening in a partition through which a rotational shaft is passed. The moving shaft tends to produce heat and frictional wear as it rotates against the sealing device. The heat created by the friction tends to degrade the elastomers and polymers in the seal so that the seal tends to shrink, harden and crack, thereby compromising the integrity of the seal. Thus, the seal has to be replaced periodically if proper sealing action is to be maintained.
The present invention differs from the prior art in that it is not a moving seal in the strict sense of the term. Rather, it is stationary in relation to both the shaft and partition; the seal does not rotate against the shaft or the partition to be sealed. The problem of shrinkage due to loss of elastomers and polymers occasioned by frictional heat is eliminated. The seal provides continuous constant sealing action.
The contemplated sealing mechanism is a continuous flexible diaphragm or membrane suitably clamped to a pair of pressure plates that are floatably positioned between two cam elements carried by separate axially aligned shafts or shaft sections. The shafts extend through separate housing plates which are clamped together to form a housing structure that closes the opening in the wall or partition. The action of the sealing diaphragm is such that when either shaft is torqued, its cam element rotates the other shaft. The floatably-positioned pressure plates wobble around the shaft axis at a rate proportional to the shaft rotational speed.
The advantage the described sealing mechanism has over the prior art is that the sealing diaphragm provides a continuous, uninterrupted seal that should not ever leak or require replacement due to wear, as occurs with moving seals. The present invention is thus suitable for sealing the personnel compartment of a military vehicle from external toxic substances .